As lithography techniques in a semiconductor element manufacturing process, a double patterning technique by means of ArF-immersion exposure, EUV lithography, nanoimprinting, and the like are known. The conventional lithography techniques have hold a variety of problems, such as cost increase and through-put deterioration in association with increased fineness of a pattern.
Under these circumstances, self-assembly (DSA: Directed Self-Assembly) has been expected to be applied to the lithography technique. Since the self-assembly occurs due to a voluntary behavior of energy stabilization, a pattern with high dimensional accuracy can be formed. In particular, a technique of applying microphase separation of a block copolymer enables formation of periodic structures in a variety of shapes of several nm to several hundred nm by simple coating and anneal processes. By transforming the block copolymer into a spherical shape, a cylindrical shape, a lamellar shape or the like in accordance with a composition ratio of its block, and changing the size of the copolymer in accordance with its molecular weight, it is possible to form a dot pattern, a hole or a pillar pattern, a line pattern, or the like, having a variety of dimensions.
In order to form a desired pattern in a broad range by means of DSA, it is of necessity to provide a guide for controlling a generation position of a polymer phase formed by self-assembly. As the guide known are: a physical guide (grapho-epitaxy) which has a concavo-convex structure and forms a microphase-separation pattern in its concave portion; and a chemical guide (chemical-epitaxy) which is formed in an underlayer of the DSA material and controls, based on a difference in its surface free energy, a formation position of the microphase separation pattern.
For example, a resist film is formed on a film to be processed, and a concave portion is formed in this resist film by photolithography, to obtain the physical guide with the concavo-convex structure. Then, a block copolymer is embedded into the concave portion of the physical guide, followed by heating. This leads to microphase separation of the block copolymer into a first polymer section formed along a side wall of the concave portion and a second polymer section formed in a central portion of the concave portion. Subsequently, the second polymer section is selectively removed, to obtain a fine hole pattern. Then, the film to be processed is processed using the resist film and the first polymer section as masks.
When the block copolymer overflows from the concave portion of the physical guide, a desired phase separation pattern is not obtained. When an amount of the block copolymer inside the concave portion of the physical guide is small, the desired phase separation pattern is not obtained or sufficient processing resistance is not obtained. Hence it has been required to apply the block copolymer such that the top surface of the block copolymer that is embedded into the concave portion of the physical guide is flush with the top surface of the physical guide (resist film).
As for an actual wafer, it is inspected whether or not the block copolymer has been appropriately embedded since fluctuations may occur in dimensions, film thickness, or shape of the physical guide due to variations in material, process, or apparatus inside a wafer, inside a wafer lot, or among wafer lots. For example, an end portion and a central portion of a circuit pattern are observed, to inspect whether an NG region exists in which the block copolymer has not been appropriately embedded.
However, since the pitch and the size of the circuit pattern are fixed, the detection sensitivity for the NG region is low, and this has made the NG-region inspection troublesome. Moreover, even in the case of the NG region being detected, it has not been possible to estimate a correction amount of the application condition.